The use of continuous drip type irrigation systems for certain crops and in particular geographical areas has increased remarkably in recent years because of inherent advantages over other irrigation methods such as sprinkling or furrow irrigation. Perhaps the most important advantage of drip irrigation is that it inherently provides for the most efficient use of available water. However, in addition, it also provides a better way to supply moisture and nutrients to many different crops and results in greater production or yield than the other irrigation techniques.
In a typical drip irrigation installation a main-distribution line connected to a supply of water is attached to a series of branch conduits or laterals that may be spaced apart to extend along rows of plants. Small openings are provided at spaced intervals along each lateral or drip emitters are connected thereto at similar intervals to allow a constant but small flow of water to trickle out of these locations near plants. Due to the inherent buildup of dirt and other deleterious material that inevitably builds up in each lateral (despite filtering of the water from the supply source) the openings or emitters in the laterals tend to get clogged up. Thus, it is necessary to flush out these lateral conduits periodically by allowing water to flow through them at a relatively high velocity for a relatively short period of time. This flushing action has the effect of scrubbing away material that may tend to block the openings in the lateral. Heretofore, it has been the practice to provide a flushing valve at the remote end of each lateral conduit which is controlled by a pilot line connected to the main distribution line. This enables all laterals to be flushed simultaneously and one attempt to provide such an arrangement is shown in U.S. Pat. No. 3,921,905. However, in this patent the flushing valve disclosed is comprised of a cylinder that retains a piston-like valve that is movable to a sealing position in response to pressure from the pilot line. The valve moves in the opposite direction to an open position to allow the flushing action to take place when pilot line pressure is reduced. In field use a major problem with this flushing valve can occur because the accumulation of dirt and slime or chemicals in the water over a period of time may eventually prevent the small piston or valve element from moving as intended within its cylinder. Thus, during a flushing cycle, not all of the flushing valves could be relied on to operate properly and the system would fail to produce the desired results.
One object of the present invention is to solve the aforesaid problem by providing an improved pilot operated flushing valve for use in drip irrigation systems.
Another object of the present invention is to provide a flushing valve for drip irrigation systems that has no moving parts and is capable of reliable operation over relatively long periods of time without replacement or maintenance.
Yet another object of the present invention is to provide a flushing valve for drip irrigation systems that is relatively easy to install and facilitates the convenient installation of a controlling pilot line.
Another object of the present invention is to provide a flushing valve for drip irrigation systems that will operate to maintain a seal on the end of a lateral conduit even if the pilot line pressure drops to well below that of the lateral line pressure.
Still another object of the present invention is to provide a flushing valve for drip irrigation systems that is particularly well adapted for ease and economy of manufacture.